1. Field of the Invention
The present invention relates to a system for measuring and automatically compenating for the distortions of a connection between a telephone apparatus and a central voice processing unit, as defined in the introductory portion of claim 1.
The invention may be applied to a telephone network in which the users may deposit voice messages in digital form, for example for a vocal postal system.
2. Description of the related art
Systems for the digital storage of messages are known, which may be selected by passing to the central unit digital codes which are generated for example by a terminal provided with a numeric keyboard and a display. The selected message is then converted into vocal form by means of a text-speech converter and passed to the caller by way of the telephone connection.
As is known, telephone connection systems are subject to some factors which cause distortion and degrading of the quality of the transmission, both because the signal transmitted is limited in frequency, so that there is a loss in respect of the information available at the source, and because the microphone and the telephone lines have a certain frequency response curve which may vary from one apparatus to another and from one line to another, and because the connection always superimposes a certain level of noise on the transmitted signal.